AN ASTON-MARTIN ROAD RACER.
WITH reference to the illustration which appeared
on the cover of our March issue, we now have pleasure in giving a few constructional details of the special Aston-Martin racer as shown above, which was built to the order of a Swiss gentleman who is well known on the Continent as a keen sporting motorist and has a preference for road racing.
In its main features the chassis conforms with that built by Messrs. Bamford & Martin, Ltd., for the French Grand Prix of 1922, but the design has been brought up to date in every way, and incorporates several interesting features. The four-cylindered engine (65 mm. bore by 112 mm. stroke) gives a cubic capacity of less than 1,500 c.c., and during bench tests developed no less than 57 B.H.P. at 3,950 revolutions per minute. Four valves per cylinder are employed, these being operated direct
from two overhead camshafts, which are driven from a vertical shaft located at the front of the engine.
Ignition is by means of a single Scintilla magneto, this make being selected as it is of Swiss origin, for which spares are more easily obtained in that country than those for other makes. One set of plugs only is fitted, each plug being located centrally in the top of the combustion chamber. A single Zenith carburettor is used.
A refinement of design is to be seen on the radiator, the wire shield for which is incorporated with the radiator casing, which, besides being very rigid, gives an improved appearance to the front of the car. Details of the front wheel brake gear may be seen from the illustration reproduced as Fig. 2. These brakes are of the Perrot type, and are actuated from the pedal ; but when the hand lever is operated, these, and two brakes on the rear wheels, come into actions
Another interesting feature connected with the brakes is the large knurled adjusters, which not only are very accessible, but actually permit of brake adjustment from the driver’s seat whilst the car is in motion. The design of the accelerator pedal is unique, for, taking the form of an inverted horseshoe embracing the
steering column, it can be actuated by either foot, thus reducing driving fatigue on long runs at high speed.
All the springs are of the semi-elliptic type, but are shorter and stiffer than usual, their action being a.ssisteg by Hartford shock absorbers. The wheel base is 9 in. shorter than that of the standard Aston-Martin chassis, and measures 8 ft. Marks steering is fitted, and the lay-out of the steering rods and levers shows that a close study has been made of cornering at high speeds. Mounted at the rear of the frame by the aid of an extra tubular cross member is a circular petrol tank with a capacity of 14 gallons.
During its preliminary tests the chassis attained a speed of 58 m.p.h. on second gear, 78 m.p.h. on third gear, and 94 m.p.h. on top gear in chassis form, which speeds will of course be considerably increased by the fitting of a semi-streamlined body.
It is capable of accelerating from a standing start to 8o m.p.h. in 18 seconds, and at 60 m.p.h. can be brought to a standstill within a distance of 40 yards.
Driving this car on the road at 65 it gives the impression one is handling a touring car at 30, as the exhaust, which is very audible at low speeds, is quite inaudible to the occupants of the car when travelling fast, and the suspension, which seems harsh at touring speeds, suits these high road speeds to perfection.
It is interesting to note that this car was completed within 17 weeks of the order, this time including the preparation of the design and the working drawings of some of the parts, and it left for Switzerland the day after our photographs were taken. Our readers will be informed as to its performance in actual racing in due course.
The design is the result of the experience of Mr. Lionel Martin, and the chassis represents an extremely fine example of automobile engineering as applied to the improvement of the modern sporting car.